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Experimental Methods tyre, there is symmetry between the left (1, 2, 3) and the right (10, 9, 8) hand side of the soil bin with the highest values in the centre (five and six). Thus measurements taken at symmetrical positions relative to the centre of the rut have similar readings and conse- quently these readings were averaged resulting in the curves shown in Figure 17 b). The curves 4+7 and 5+6 in Figure 17 b) coincide so giving the possibility of averaging them and thus creating one penetrometer resistance curve per treatment representing the average of the centre 4 points of measurements or the centre 360 mm of the rut. This mean curve is shown in Figure 17 c). The same procedure was applied for the initial control. 2.2.3 Dry Bulk Density Two different methods to determine dry bulk density were used. In the soil bin only a density ring was utilized and in the field measurements both, a density ring and a gamma ray probe (Troxler) were used. 2.2.3.1 Gravimetrical Density Measurement Dry bulk density (DBD) was measured gravimetrically at depths of 0, 250, and 500 mm, with three replications before and after each run, at the centre of the track mark in the soil bin. A cylindrical ring (60 mm diameter and 51.5 mm deep) was pushed into the soil and excavated. The surplus soil was carefully cut off and the soil sample from the cylinder weighed and dried for 48 h at 105 o C. The dry soil was weighed and soil water content determined from the weight difference. Dry bulk density was calculated from the given volume of the cylinder and the dry weight. 2.2.3.2 Nuclear Density Measurement Gauge With the aim to gain a more precise resolution of the increase in soil density a nuclear density gauge, namely a Troxler 3430, was used to measure soil density. With this measurement device a gamma source is positioned at a known depth in the soil in a previously created access hole. Once the gamma source is in position and switched to transmitting mode, the detectors located within the gauge count the received radiation, which depends on the dry bulk density and the depth of location of the source within the soil. From this the ma- Ph.D. Thesis Dirk Ansorge (2007) 24
Experimental Methods chine derives the average dry bulk density which is mainly influenced by the DBD at the position where the source is located (Gameda et al., 1987). Figure 18 shows the used Trox- ler. As this is a radioactive measurement device the measurements were subcontracted to ACS Testing, Ltd, Dorset, BH16 6LE. The absolute accuracy of a Troxler 3430 is not very high in determining DBD, however, the experiment is set up to determine relative differences between the single treatments and therefore the device should be suitable (ACS, 2006). Gameda et al. (1987) derived a similar conclusion when comparing a single probe (like the Troxler) to a dual probe (whereby both transmitter and recorder are located within the soil at the same depth a given distance apart from each other). Overall the dual probe showed a higher accuracy, but both methods gave consistent results. In determining absolute dry bulk density the authors suggest that each type had to be calibrated on a soil with known density before it is taken to the field to gain accurate absolute dry bulk density readings. As the aim of this field experiment is to accomplish a relative comparison of treatments by measuring dry bulk density before and afterwards it is not necessary to do a calibration. Following Gameda et al. (1987) the vital assumption of consistency of readings within one soil type is provided. The marked ruts before the run and the places of measurements for the Troxler and the fishing hooks including the reference surface are shown in Figure 19. Figure 18: The Troxler on a field plot Ph.D. Thesis Dirk Ansorge (2007) 25
Page 1 and 2: Cranfield University School of Appl
Page 3 and 4: Abstract Ancillary experiments show
Page 5 and 6: Table of Contents TABLE OF CONTENTS
Page 7 and 8: Table of Contents 4.1.3 Analysis of
Page 9 and 10: Table of Contents 11.1.1.1 Comparis
Page 11 and 12: List of Figures and Tables Figure 3
Page 13 and 14: List of Figures and Tables Figure 1
Page 15 and 16: Nomenclature NOMENCLATURE Abbreviat
Page 17 and 18: Introduction 1 INTRODUCTION 1.1 Bac
Page 19 and 20: Introduction � Ansorge, D. and Go
Page 21 and 22: Introduction 1.2 Aim To elucidate t
Page 23 and 24: Introduction a) the soil compaction
Page 25 and 26: Experimental Methods 2.1.1.1 Test F
Page 27 and 28: Experimental Methods had been mount
Page 29 and 30: Experimental Methods track; the loa
Page 31 and 32: Experimental Methods 800/10.5/2.5 t
Page 33 and 34: Experimental Methods term. In the m
Page 35 and 36: Experimental Methods Soil Surface F
Page 37 and 38: Experimental Methods Depth (cm) 0 1
Page 39: Experimental Methods ence surface c
Page 43 and 44: Experimental Methods depth. The dat
Page 45 and 46: Experimental Methods with water and
Page 47 and 48: Experimental Methods 2.4 Statistica
Page 49 and 50: Laboratory Studies Into Undercarria
Page 77 and 78: Field Study With Full Size Combine
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Field Study With Full Size Combine
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Alleviation of Soil Compaction Howe
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Alleviation of Soil Compaction not
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Alleviation of Soil Compaction in a
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Alleviation of Soil Compaction diff
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Soil Compaction Models sibilities t
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Soil Compaction Models depends on t
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Soil Compaction Models Wroth (1968)
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Soil Compaction Models however, the
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Soil Compaction Models level. Criti
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Soil Compaction Models Utilizing Ke
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Soil Compaction Models average of m
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Soil Compaction Models Depth (mm) -
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Soil Compaction Models ture content
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Soil Compaction Models with four ot
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Soil Compaction Models Predicted In
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Soil Compaction Models Depth (mm) -
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Soil Compaction Models and 13.7 % b
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Soil Compaction Models Rel. Density
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Soil Compaction Models VCL paramete
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Soil Compaction Models The approach
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Soil Compaction Models surface stay
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Soil Compaction Models This result
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Soil Compaction Models 6.6.1.3 Wate
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Soil Compaction Models σσ 1 (kPA)
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Soil Compaction Models pressure to
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Soil Compaction Models The response
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Soil Compaction Models On medium so
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Soil Compaction Models SOILFLEX tak
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Ancillary Experiments 7 ANCILLARY E
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Ancillary Experiments Average conta
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Ancillary Experiments In order to c
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Ancillary Experiments contrary, the
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Ancillary Experiments Figure 102: S
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Ancillary Experiments track and the
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Ancillary Experiments even when hav
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Ancillary Experiments 7.3.2 Influen
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Ancillary Experiments The results f
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Ancillary Experiments Figure 117: S
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Ancillary Experiments Contact Press
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Ancillary Experiments Figure 123: F
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Ancillary Experiments Sinkage (mm)
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Ancillary Experiments model which o
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Ancillary Experiments 7.3.5 The Inf
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Ancillary Experiments 7.3.7 Discuss
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Ancillary Experiments Terzaghi (194
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Ancillary Experiments contact area.
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Ancillary Experiments soil forward
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Conclusions � The longitudinal so
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Bibliography 10 BIBLIOGRAPHY Aboaba
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Bibliography Defossez, P., Richard,
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Bibliography Gregory, A.S.; Whalley
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Bibliography Lamande, M., Schjonnin
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Bibliography Seig, D., 1985. Soil C
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Appendix 11 APPENDIX Ph.D. Thesis D
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Appendix Figure 32: VCL sample at t
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Appendix comparison at the deepest
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Appendix Estimated Pressure (kPa) 2
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Appendix 11.1.1.2.1 SOCOMO One of t
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Appendix by Seig (1985) who showed
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Appendix Soil water content 15 % an
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Appendix Adapting critical state so
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Appendix density is obtained by add
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Appendix Table 5: Values of constan
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Appendix choice of a concentration
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Appendix 11.1.3.1 Dense/Hard and Lo
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Appendix 11.1.3.2 Stratified Soil C
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Appendix To summarize the ability t
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Appendix In the following the predi
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Appendix concentration factor of 4,
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Appendix 11.1.5.1 Confining Pressur
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Appendix Figure 24. The VCL created
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Appendix Rel. Density 2 1,9 1,8 1,7
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Appendix relation of � 1 to � 2
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Appendix Rel. Density 2 1,9 1,8 1,7
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Appendix Rel. Density 1,7 1,68 1,66
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Appendix Depth (mm) 0,0 100,0 200,0
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Appendix Figure 42: Plate in cookin
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Appendix � z � � �� k c p
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Appendix Table 8: n and k depending
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Appendix to the plate sinkage equat
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Appendix with a slight deviation fr
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Appendix Table 12: DBD values for a
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